<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="../css/reset.css">
    <style>
        .header {
            height: 100px;
            background-color: #f00;

            position: fixed;
            top: 0;

            /* 需要写宽度 ， 不占位置，他后面的盒子需要写margin-top 把位置留出来 */
            width: 100%;
        }

        h1 {
            margin-top: 100px;
        }
    </style>
</head>

<body>
    <div class="header"></div>

    <h1>111111111111111111111111111</h1>
</body>

</html>